Loudspeaker

ABSTRACT

Loudspeaker with a cabinet in the form of a bent tube having a loudspeaker element at one end and a closure plate at the other end, whereby sound reproduction will be of very high quality although the tube is relatively small in size compared with conventional loudspeaker cabinets.

Nilsson et a1.

1 1 LOUDSPEAKER [75] Inventors: Lars-Goran Bernhard Nilsson,

Dalby; Bengt Jiirgen Tyke Tykesson, Lund, both of Sweden [73] Assignee:Jan Einar Bostedt, Lund, Sweden;

by said Nilsson [22] Filed: Apr. 3, 1972 [21] App]. No.: 240,726

[30] Foreign Application Priority Data Feb. 29, 1972 Sweden 2475/72 52us. Cl 181/31 B [51] Int. Cl G10k 13/00, 1-104r 1/28 [58] Field ofSearch 181/31 B [56] References Cited UNITED STATES PATENTS 2,775,30912/1956 Villchur 181/31 B 51 Oct. 30, 1973 3,393,766 7/1968 Mitchell181/31 B FOREIGN PATENTS OR APPLICATlONS 1,084,764 7/1960 Germany 181/31B 653,263 5/1951 Great Britain 181/31 B 628,901 11/1961 ltaly [81/31 BPrimary Examiner-Stephen J. Tomsky Att0rney E. F. Wenderoth et a1.

10 Claims, 4 Drawing Figures LOUDSPEAKER This invention relates to aloudspeaker having a cabinet which contains at least one loudspeakerelement, damping material and possibly a dividing filter.

Conventional loudspeakers for high-quality sound reproduction generallyrequire a very large space as well as a plurality of loudspeakerelements of various types, which are very costly. One of the drawbacksof prior art loudspeakers the cabinets of which as a rule have planarand acute angles, is that the rearwardly directed sound wave from theloudspeaker element reaches the rear wall of the cabinet (the shortestdistance) and then along with other sound waves of different intensitythe bottom of the cabinet. While travelling this distance a majorportion of the acoustical energy will be consumed as it is convertedinto frictional heat in the damping material of the cabinet, whichconsiderably reduces the efficiency. I

The object of the invention is to provide a loudspeaker of very highsound reproduction quality though of relatively compact size comparedwith prior art loudspeakers, and also at relatively low costs.

To this end, the cabinet of the loudspeaker of the type outlined in theforegoing is in the form of a bent tube which has one end closed bymeansof a plate while the loudspeaker element is positioned at the other endof the tube.

One embodiment of the present invention will be more fully describedhereinbelow with reference to the accompanying drawings in which:

FIG. 1 is a section of a loudspeaker according to the invention;

FIG. 2 is a side view of the loudspeaker in FIG. 1, certain parts havingbeen removed for greater clarity;

FIG. 3 is a wiring diagram of connecting elements and a dividing filtercomprised in the loudspeaker shown in FIG. 1;

FIG. 4 shows a frequency response recorded with the loudspeaker shown inFIG. 1

The loudspeaker illustrated in FIG. 1 has a cabinet 1 which consists ofawtube of circular cross section. The tube is'bent at an angle of 90, asis shown by means of the crossing axes a and b. The axis b isapproximately half as long'as the axis 0. One end 'of the tubeis closedby means ofa plate 2 of lead or other soft, dense metal which is securedin the tube in some suitable conventional manner. For additionalstability, a lead weight 9 can be positioned, as shown. A loudspeakerelement 3 is mounted in a baffle plate 4. The loudspeaker element 3preferably is of the bass type and the baffle plate 4 is fastened in thetube in some suitable manner. Ahead of the loudspeaker element 3 ismounted a further loudspeakerelement 5 which is of the treble type andheld in position by means of some suitable fastening mem ber 6. Somesuitable material, such as loudspeaker cloth or a metal grid 7 of-somesuitable kind, is applied over the loudspeaker end of the tube 1. Adamping material 8 is disposed in the interior of the cabinet rearwardlyof the loudspeaker element 3. This damping material is a syntheticlong-filament sound absorbing material which is previously known in theloudspeaker technique and has proved to prevent partial vibrations.

The two loudspeaker elements 3 and 5 are connected in the mannerillustrated in FIG. 3, the bass loudspeaker element 3 being connectedover two input terminals 10 and 11; the input terminal 10 is connectedto i earth at 14. The treble loudspeaker element 5 is connected inseries with a resistor 12 and a capacitor 13. This series circuit isconnected over the input terminals 10 and 11 and thus lies in parallelwith the loudspeaker element 6. This dividing filter shown at 15 in FIG.1 thus is an RC-filter.

FIG. 4 illustrates a frequency response which has been recorded with aloudspeaker having the following data frequency response: 55-20,000 Hzpower: 15 W sin (1 kHz 10 min) impedance: 8 ohm, 1 kHz self-resonance(fO about Hz loudspeaker elements: one 5-inch bass loudspeaker withrubber-mounted cone one l-inch treble loudspeaker with largedistributing angle sensitivity: 5 W (1 m, 1 kHz, 0 96 dB) volume: about4 litres weight: about 7 kg dividing frequency: 5125 Hz The greatadvantage of the loudspeaker according to the present invention is thatas large a part as possible of the rearwardly directed sound wave is leddown into the base (floor, furniture or the like) without any greaterlosses. This is permitted by the round cross sectional area of theloudspeaker cabinet and the gently rounded bend or curvature of the tubewhereby the rearwardly directed sound wave is uniformly damped so thatall critical frequencies are uniformly damped. The distance between theloudspeaker element 3 and the wall of the tube 1 is such that therearwardly directed sound wave is not influenced in its critical pointin which the energy of the sound wave is at its maximum.

The length of the tube is adapted to the selfresonance of the bassloudspeaker in the system or H] 6 fO converted into meters 330/ 16 fO inorder that the cabinet shall be as small as possible (fO 80 Hz). As willappear from FIG. 1, the treble loudspeaker element 5 is placed as far infront as possible at one end of the tube in order to obtain a maximumdistribution of the treble and the bass loudspeaker element 3 is placedas close as possible to the treble loudspeaker element 5 in order thatthe distribution of the intermediate register and the inner volume inthe tube 1 shall be as large as possible and arising interference assmall as possible. As already mentioned, the dividing filter is of theRC type and this filter gives a well defined dividing frequency, a smallintermodulation distorsion and insignificant influence on the dampingfactor of the amplifier. The tube is preferably made from syntheticplastics in some suitable manner.

What we claim and desire to secure by Letters Patent l. A loudspeakersystem comprising a cabinet in the form ofa rigid tube bent at an angleso as to form a first tube section and a second tube section, the crosssection of said tube being in the form of a closed curve, the end ofsaid tube at said first tube section being closed by a plate meansincluding a soft, dense metal and a loudspeaker means being positionedat the end of said second tube section at the other end of said tube;and damping means covering substantially all of the inner walls of saidcabinet.

2. A loudspeaker system as claimed in claim I wherein said tube is bentat substantially right angles so as to form said first and second tubesections.

I wherein said loudspeaker means comprises two loudspeaker elements andsaid system further includes a dividing filter connecting said twoloudspeaker elements together.

7. A loudspeaker system as claimed in claim 6 wherein one of said twoloudspeaker elements is of the bass type and the other of said twoloudspeaker elements is of the treble type; said bass type loudspeakerelement being positioned centrally at the end 'of said second tubesection and said treble type loudspeaker element being positioned infront of and coaxially with said bass type loudspeaker element.

8. A loudspeaker system as claimed in claim 7 wherein the length of saidsecond tube section is greater than the length of said first tubesection.

9. A loudspeaker system as claimed in claim 7 wherein the ratio of thelengths of said first and second tube sections is 1:2.

10. A loudspeaker system as claimed in claim 7 wherein said tube iscylindrical.

1. A loudspeaker system comprising a cabinet in the form of a rigid tube bent at an angle so as to form a first tube section and a second tube section, the cross-section of said tube being in the form of a closed curve, the end of said tube at said first tube section being closed by a plate means including a soft, dense metal and a loudspeaker means being positioned at the end of said second tube section at the other end of said tube; and damping means covering substantially all of the inner walls of said cabinet.
 2. A loudspeaker system as claimed in claim 1 wherein said tube is bent at substantially right angles so as to form said first and second tube sections.
 3. A loudspeaker system as claimed in claim 1 wherein the length of said second tube section is greater than the length of said first tube section.
 4. A loudspeaker system as claimed in claim 1 wherein the ratio of the lengths of said first and second tube sections is 1:2.
 5. A loudspeaker system as claimed in claim 1 wherein said tube is cylindrical.
 6. A loudspEaker system as claimed in claim 1 wherein said loudspeaker means comprises two loudspeaker elements and said system further includes a dividing filter connecting said two loudspeaker elements together.
 7. A loudspeaker system as claimed in claim 6 wherein one of said two loudspeaker elements is of the bass type and the other of said two loudspeaker elements is of the treble type; said bass type loudspeaker element being positioned centrally at the end of said second tube section and said treble type loudspeaker element being positioned in front of and coaxially with said bass type loudspeaker element.
 8. A loudspeaker system as claimed in claim 7 wherein the length of said second tube section is greater than the length of said first tube section.
 9. A loudspeaker system as claimed in claim 7 wherein the ratio of the lengths of said first and second tube sections is 1:2.
 10. A loudspeaker system as claimed in claim 7 wherein said tube is cylindrical. 